The invention concerns a device for controlling a by-pass valve in a diesel engine for driving a vehicle. The by-pass valve is located in a gas duct in the cylinder head of the diesel engine between a combustion space of at least one cylinder and an exhaust gas conduit upstream of a soot burn-off filter and from which, as a function of operating parameters of the diesel engine, a fuel/air mixture ignited in the combustion space can flow into the exhaust gas conduit to regenerate the soot filter.
A diesel engine with a by-pass duct between a combustion space and the exhaust gas installation is known from U.S. Pat. No. 4,380,149. In that arrangement, it is possible to open and close the by-pass duct by means of a solenoid valve and control takes place as a function of operating parameters. This by-pass duct, which is formed by a passage hole between the pre-combustion chamber and the exhaust manifold, permits ignited fuel/air mixture to flow at high velocity directly into a soot filter located in the exhaust manifold after the solenoid valve has been opened and, by this means, ignites the soot particles which have collected in the soot filter. A disadvantageous feature, however, is that the device described can only be used for igniting a soot filter which is located directly in the immediate zone of action of the flame emerging from the by-pass duct, i.e. directly in the exhaust manifold. It is similarly disadvantageous that, in order to operate the device, an expensive solenoid valve which has to be opened for a short time at the moment of injection with exactly the cyclic frequency of the engine is necessary--together with a device for the corresponding control of the solenoid valve.
In diesel engines which have a throttle butterfly in the exhaust conduit as an engine brake device, it is also known from German Patent Document 34 28 626 to locate additional by-pass conduits between the combustion space and the exhaust gas conduit for a further increase in the engine braking power, it being possible to open and close each of the by-pass conduits by means of a fixed area throttle valve.
An object of the present invention is to provide a device for controlling a by-pass valve that in a simple and low-cost manner such that the by-pass valve can be used as an engine brake valve for engine braking operation in addition to being used as a control to initiate the regeneration of the soot burn-off filter.
This and other objects are achieved by the present invention which provides a device for controlling at least one by-pass valve in a diesel engine for driving a vehicle. The by-pass valve is located in a gas duct in a cylinder head of the diesel engine between a combustion space of at least one cylinder and an exhaust gas conduit upstream of a soot burn-off filter and from which, as a function of operating parameters of the diesel engine, a fuel/air mixture ignited in the combustion space can flow into the exhaust gas conduit to regenerate the soot filter. One by-pass valve is located on each cylinder head of the diesel engine and the by-pass valves are additionally drivable to increase the engine braking power. All the by-pass valves are driven into an open position in order to increase the engine braking power and, for regenerating the soot burn-off filter, only some of the by-pass valves are driven into an open position by a control unit as a function of parameters relating to regeneration phases of the soot burn-off filter.
Using a relatively simple and low-cost device, the present invention allows the by-pass valve to be used for regenerating the soot burn-off filter as a function of operating parameters, as well as for controlling the engine braking power.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.